1. Field of the Invention
The present invention relates to a mechanism for actuating a deflector of a Pelton wheel (turine or unit) and more particularly to such a mechanism of the type in which an electric servomotor is used to maintain the deflector in its opened position, and the stored energy of a spring is used to close the deflector.
2. Description of the Prior Art
A Pelton wheel is of a type of impulse turbine and is usually operated from a high-head source ranging from 200 to 1,800 meters when the volume of water available is relatively small. The water under pressure which is introduced into the casing of the Pelton wheel is accelerated when it is forced to flow through a nozzle and then the resulting high-velocity jet impinges on the buckets of the turbine wheel or runner, whereby the runner is rotated. A deflector is disposed at the discharge end of the nozzle pipe so that in the case of an emergency, the high-velocity jet emerging from the nozzle is deflected and thereby prevented from impinging on the buckets of the runner. A mechanism which uses a fluid operated servomotor for opening and closing the deflector has been well known in the art, but the fluid operated servomotor needs not only a source for supplying oil under pressure but also a device for controlling the pressure of the working oil so that there arises the problem of such associated or auxiliary equipment becoming complicated in construction and large in size for the output of the Pelton wheel. In addition, in the case of a system in which a fluid operated servomotor is activated to push an operating rod to close the deflector, there arises a problem in that a large force due to high hydraulic pressure acts on the rod in its axial direction, causing buckling of the operating rod.
In order to solve the above described problems, there has been proposed a system in which a fluid operated servomotor is combined with a coiled spring so that the deflector is moved to and maintained at the opened position by the fluid operated servomotor and, in the case of an emergency, the operating rod is actuated by the force of the coiled spring, thereby closing the deflector (Fuji Jiho, Vol. 55, No. 5, Page 30, published in 1982). However, according to the above-described prior art system, the force of the coiled spring is exerted on the operating rod in the direction in which the operating rod is compressed, so that there arises the problem of unavoidable buckling of the operating rod.